The experimental set-up
Contact: anders.madsen@xfel.eu
The Materials Imaging and Dynamics (MID) instrument [1] provides ultrafast hard X-ray scattering and imaging capabilities at European XFEL [2,3] with focus on applications of the coherence properties of the beam. The setup allows for pumping the samples with infrared or optical femtosecond lasers and working with nanosized focused X-ray beams. The instrumentation comprises a megapixel area detector, AGIPD [4], with MHz acquisition rate and a multi-purpose sample chamber (MPC) that can host various sample environments in air or under vacuum. MID can operate with 15 fs SASE pulses (bandwidth ~2×10-3) or in a self-seeded mode with 10-4 bandwidth pulses. The techniques available at MID range from X-ray photon correlation spectroscopy over ultrafast pump-probe diffraction to holographic and phase-contrast imaging and X-ray microscopy. Mössbauer spectroscopy and fluorescence correlation imaging are also possible.
For this experiment, the AGIPD detector was positioned in large field-of-view (LFOV) geometry 17 cm from the liquid jet. A photon energy of 23 keV allowed measuring scattering vectors in the range of 1–9 Å-1
The MID instrument [1,5] in LFOV configuration. The AGIPD detector can be directly connected to the multi-purpose sample chamber (MPC), hence providing a small sample-detector distance, when the detector arm is placed in the forward scattering direction. The X-ray beam is entering the MPC from the left side.
In LFOV mode, a large range of scattering angles, and hence scattering vectors, can be captured in a single AGIPD frame.
Diffraction image from crystalline Kr delivered in a cryo-cooled jet to interact with the XFEL beam. Scattering rings correspond to the (111) and (200) fcc reflections and the streaks are due to crystalline defects [6]
Nearfield holography is pursued at MID as well.
Reconstructed phase image of a near-field hologram. Shown is the break-up of a water jet filament 16 ns after being hit by an infrared laser pulse. The red arrows indicate the fronts of the resulting shockwave. The scale bar is 20 µm [7].
[1] A. Madsen et al., J. Sync. Rad. 28, 637 (2021)
[2] T. Tschentscher et al., Appl. Sci. 7, 592 (2017)
[3] W. Decking et al., Nat. Photon. 14, 391 (2020)
[4] A. Allahgholi et al., Nucl. Instr. and Meth. A 942, 162324 (2019)
[5] Video: The MID instrument at the European XFEL
[6] J. Möller, R. Grisenti et al., submitted (2023)
[7] J. Hagemann et al., J. Sync. Rad. 28, 52 (2021)